Cell search method and terminal device

ABSTRACT

Provided are a cell search method and a terminal device. The method includes that a terminal device searches a cell to camp on, wherein the terminal device is in an inactive state, and searches for an acceptable cell and/or a suitable cell when the terminal device does not find any suitable cell to camp on, wherein the acceptable cell is a cell on which the terminal device is capable of camping and only obtaining a limited service, and the suitable cell is a cell on which the terminal device is capable of camping and obtaining a normal service, and when searching for an acceptable cell and/or a suitable cell, continues to maintain the inactive state and a timer, wherein the timer is a location update timer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 16/878,216, filed May 19, 2020, which is the continuationapplication of International Application No. PCT/CN2018/074493 filed onJan. 29, 2018. The entire contents of above identified applications arehereby incorporated by reference.

TECHNICAL FIELD

Implementations of the present disclosure relate to the communicationfield, and more particularly, to a cell search method and a terminaldevice.

BACKGROUND

With people's pursuit of rate, latency, high-speed mobility and energyefficiency, and due to diversity and complexity of services in futurelife, International Standards Organization of 3rd Generation PartnershipProject (3GPP) began to research and develop a 5-Generation mobilecommunication technology (5G). To reduce air interface signaling,quickly resume radio connection and quickly resume data service, a newRadio Resource Control (RRC) state, namely a radio resource controlinactive (RRC_INACTIVE) state, is defined in a 5G network environment.

When a User Equipment (UE) is in the RRC_INACTIVE state, a network sideconfigures a paging area of a Radio Access Network (RAN) for the UE.When the UE moves within the paging area, the network side is notnotified, and a mobility behavior under RRC_IDLE, i.e., a cell selectionand reselection principle, is followed. When the UE moves out of thepaging area, the UE is triggered to resume a RRC connection andre-obtain a paging area configured by the network side.

When a cell signal is not good, the UE in the INACTIVE state may beunable to find a suitable cell to reside in, and the UE may enter anarbitrary cell search state or may choose an acceptable cell to residein. It can be found that how to control a state and context of the UEand how to ensure that a UE's behavior is manageable and controllable isan urgent problem to be solved.

SUMMARY

A cell search method and a terminal device are provided.

In a first aspect, a cell search method is provided, which is applied toa terminal device in an inactive state, wherein the inactive staterefers to that the terminal device is disconnected from a networkdevice, and both the network device and the terminal device retaincontext information of the terminal device, wherein the contextinformation is used for establishing a connection between the terminaldevice and the network device; the method includes that the terminaldevice enters an arbitrary cell search state to search for an acceptablecell and/or a suitable cell when the terminal device does not search outany suitable cell to reside in, wherein the acceptable cell is a cell inwhich the terminal device is capable of residing and only obtaining arestricted service, and the suitable cell is a cell in which theterminal device is capable of residing and obtaining a normal service.

In an embodiment of the present invention, when no suitable cell issearched out to reside in by a terminal device in the INACTIVE state,the terminal device searches for an acceptable cell and/or a suitablecell by entering an arbitrary cell search state.

In some possible implementations, the method further includes that whensearching out the acceptable cell, the terminal device resides in theacceptable cell and continues to search for the suitable cell.

In some possible implementations, the method further includes that whenentering the arbitrary cell search state, the terminal device starts afirst timer; when the first timer expires and no suitable cell issearched out, the terminal device enters an idle state and deletes thecontext information; and when the first timer does not expire and thesuitable cell is searched out, the terminal device stops the first timerand resides in the suitable cell.

In some possible implementations, before the terminal device starts thefirst timer, the method further includes that the terminal devicereceives configuration information sent by the network device, whereinthe configuration information is used for the terminal device toconfigure the first timer.

In some possible implementations, the configuration information isinformation configured for the terminal device when the network deviceinstructs the terminal device to enter the inactive state.

In some possible implementations, the method further includes that whenentering the arbitrary cell search state, the terminal device enters theidle state and deletes the context information.

In some possible implementations, the method further includes that whenentering the arbitrary cell search state, the terminal device continuesto maintain the inactive state and a second timer, wherein the secondtimer includes a location update timer.

In some possible implementations, the method further includes that whenthe second timer expires, the terminal device enters the idle state anddeletes the context information.

In some possible implementations, the method further includes that afterentering the idle state and deleting the context information, theterminal device continues to maintain the arbitrary cell search state.

In the embodiment of the present invention, when no suitable cell issearched out to reside in by the terminal device in the INACTIVE state,the terminal device searches for an acceptable cell and/or a suitablecell by entering an arbitrary cell search state.

In a second aspect, a terminal device is provided, wherein the terminaldevice is in an inactive state, the inactive state refers to that theterminal device is disconnected from a network device, and both thenetwork device and the terminal device retain context information of theterminal device, the context information is used for establishing aconnection between the terminal device and the network device; theterminal device includes a processing unit.

Herein, the processing unit is configured to enter an arbitrary cellsearch state to search for an acceptable cell and/or a suitable cellwhen the terminal device does not search out any suitable cell to residein, wherein the acceptable cell is a cell in which the terminal deviceis capable of residing and only obtaining a restricted service, and thesuitable cell is a cell in which the terminal device is capable ofresiding and obtaining a normal service.

In a third aspect, a terminal device is provided, wherein the terminaldevice is in an inactive state, the inactive state refers to that theterminal device is disconnected from a network device, and both thenetwork device and the terminal device retain context information of theterminal device, the context information is used for establishing aconnection between the terminal device and the network device; theterminal device includes a processor.

Herein, the processor is configured to enter an arbitrary cell searchstate to search for an acceptable cell and/or a suitable cell when theterminal device does not search out any suitable cell to reside in,wherein the acceptable cell is a cell in which the terminal device iscapable of residing and only obtaining a restricted service, and thesuitable cell is a cell in which the terminal device is capable ofresiding and obtaining a normal service.

In a fourth aspect, a computer readable medium is provided for storing acomputer program thereon. The computer program includes instructionsused for performing the method implementation of the above first aspect.

In a fifth aspect, a computer chip is provided. The computer chipincludes an input interface, an output interface, at least oneprocessor, and a memory. The at least one processor is used forexecuting codes in the memory. When the codes are executed, theprocessor may implement various processes executed by the terminaldevice in the cell search method of the above first aspect and variousimplementations.

In a sixth aspect, a communication system is provided, which includesthe above terminal device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an example of a communication system according to animplementation of the present disclosure.

FIG. 2 is a schematic flowchart of a cell search method according to animplementation of the present disclosure.

FIG. 3 is a schematic block diagram of a terminal device according to animplementation of the present disclosure.

FIG. 4 is another schematic block diagram of a terminal device accordingto an implementation of the present disclosure.

DETAILED DESCRIPTION

Implementations of the present disclosure may be applied to anycommunication system including a terminal device in an RRC_INACTIVEstate. That is, the communication system 100 is only for exemplarydescription of the implementations of the present disclosure. However,the implementations of the present disclosure are not limited to it.

Technical solutions of implementations of the present disclosure may beapplied to various communication systems, for example, a Global Systemof Mobile Communication (GSM) system, a Code Division Multiple Access(CDMA) system, a Wideband Code Division Multiple Access (WCDMA) system,a General Packet Radio Service (GPRS), a Long Term Evolution (LTE)system, LTE Time Division Duplex (TDD), a Universal MobileTelecommunication System (UMTS), 5G.

Herein, main application scenarios of 5G are Enhance Mobile Broadband(eMBB), Ultra-Reliable and Low Latency Communication (URLLC), andmassive Machine Type of Communication (mMTC). The eMBB aims at users'obtaining multimedia contents, services and data. In addition, as theeMBB may be deployed in different scenarios, capabilities andrequirements thereof are quite different, for example, indoor, urban,rural areas. Typical applications of the URLLC include industrialautomation, power automation, telemedicine operation (surgery), trafficsafety, etc. Typical characteristics of the mMTC include high connectiondensity, small amount of data, latency insensitive services, low costand long life of a module, etc.

The present disclosure describes various implementations in connectionwith a network device and a terminal device.

Herein, the network device may refer to any entity at a network side forsending or receiving signals. For example, the network device may be auser equipment of Machine Type Communication (MTC), a Base TransceiverStation (BTS) in GSM or CDMA, a NodeB in WCDMA, an Evolution Node B (eNBor NodeB) in LTE, a base station device in a 5G network, etc.

In addition, the terminal device may be any terminal device.Specifically, the terminal device may communicate with one or more corenetworks through a radio access network (RAN), and may be referred to asan access terminal, a User Equipment (UE), a subscriber unit, asubscriber station, a mobile station, a remote station, a remoteterminal, a mobile device, a user terminal, a terminal, a wirelesscommunication device, a user agent, or a user device. For example, theterminal device may be a cellular phone, a cordless phone, a SessionInitiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, aPersonal Digital Assistant (PDA), a handheld device or a computingdevice with a wireless communication function, or other processingdevice connected to a wireless modem, a vehicle-mounted device, awearable device, and a terminal device in a 5G network, or the like.

FIG. 1 is a schematic diagram of a communication system according to animplementation of the present disclosure.

As shown in FIG. 1, a communication system 100 may include a terminaldevice 110 and a network device 120. The network device 120 maycommunicate with the terminal device 110 via an air interface.Multi-service transmission is supported between the terminal device 110and the network device 120. Herein, the terminal device 110 may be in anRRC_INACTIVE state.

The RRC_INACTIVE state is different from an RRC_IDLE state and anRRC_ACTIVE state.

To facilitate understanding of a solution, the following is a briefintroduction to states of the terminal device.

In implementations of the present disclosure, states of the terminaldevice 110 may include an RRC_IDLE state, an RRC_ACTIVE state, and anRRC_INACTIVE state.

For the RRC_ACTIVE state, there is an RRC connection between theterminal device and the network device, the network device and theterminal device store context information of the terminal device. Alocation of the terminal device acquired by the network device is at aspecific cell level, mobility of the terminal device is controlled bythe network device. For the RRC_IDLE state, there is no RRC connectionbetween the terminal device and the network device, and the networkdevice does not store the context information of the terminal device.When the terminal device needs to be paged, a core network initiatespaging, and the core network configures a paging area, and mobility ofthe terminal device is based on cell selection or cell reselection bythe terminal device.

However, for the RRC_INACTIVE state, there is a connection between thecore network (CN) and the network device, context information of theterminal device exists on a certain network device. Paging is triggeredby a Radio Access Network (RAN), and the RAN manages paging areas of theRAN, that is, a location of the terminal device acquired by the networkdevice is at a paging area level of the RAN, and mobility of theterminal device is based on cell selection or cell reselection by theterminal device. In other words, the terminal device in the RRC_INACTIVEstate is disconnected from the network device, and the network deviceretains the context information of the terminal device, and the contextinformation is used for quickly establishing a connection between theterminal device and the network device.

For example, assuming that a terminal device is in the RRC_INACTIVEstate, a network device configures a paging area of the RAN for theterminal device, and the paging area of the RAN may include multiplecells. For convenience of description, in an implementation of thepresent disclosure, alternatively, the paging area of the RAN may bereferred to as an initial paging area, or a paging area preconfiguredfor the terminal device by the network device may be referred to as theinitial paging area. In other words, when performing cell reselection,the terminal device may be triggered to resume a RRC connection based onthe initial paging area.

When a cell signal is not good, the UE in the INACTIVE state may beunable to find a suitable cell to reside in, and the UE may enter anarbitrary cell search state or may choose an acceptable cell to residein. It can be found that how to control a state and context of the UEand how to ensure that a UE's behavior is manageable and controllable isan urgent problem to be solved.

To solve the above-mentioned problems, an implementation of the presentdisclosure provides a cell search method. When a cell signal is not goodduring a moving process of a UE in an INACTIVE state, by specifying astate and context information of the UE, it is ensured that the UE'sbehavior is manageable and controllable.

FIG. 2 is a schematic flowchart of a method for a terminal device tosearch a cell according to an implementation of the present disclosure.

It should be understood that the method for a terminal device to selecta cell in the implementation of the present disclosure may be applied tothe terminal device in an inactive state. The inactive state refers tothat the terminal device is disconnected form a network device, and boththe network device and the terminal device retain context information ofthe terminal device, wherein the context information is used forestablishing a connection between the terminal device and the networkdevice.

As shown in FIG. 2, the method includes acts 210-220.

In 210, a terminal device starts a search for a suitable cell.

In 220, when the terminal device does not search out any suitable cell,the terminal device enters an arbitrary cell search state to search foran acceptable cell and/or a suitable cell, wherein the acceptable cellis a cell in which the terminal device is capable of residing and onlyobtaining a restricted service, and the suitable cell is a cell in whichthe terminal device is capable of residing and obtaining a normalservice.

In addition, service types and cell classifications under the RRC_IDLEstate are explained below.

In an implementation of the present disclosure, the service types in theRRC_IDLE state include but are not limited to the following singleservice types: a restricted service, a normal service, and an operatingpersonnel service.

Restricted service: it means an emergency call made in an acceptablecell.

Normal service: it means normal use in a suitable cell.

Operating personnel service: it is used by operating personnel on areserved cell.

Implementations of the present disclosure include but are not limited tothe following cell types according to services provided.

Acceptable cell: restricted service (Emergency Call) is available in theacceptable cell.

Suitable cell: UE can reside and obtain normal services in the suitablecell.

Barred cell: the barred cell is a cell indicated as barred in systeminformation.

Reserved cell: the reserved cell is a cell indicated as reserved insystem information.

Cell selection generally occurs after Public Land Mobile Network (PLMN)selection, and its purpose is to enable a UE to select a cell whosechannel quality meets a condition to reside in as soon as possible afterpowered on. Cell selection mainly includes two types.

Further, when the terminal device searches out the acceptable cell, theterminal device resides in the acceptable cell and continues to searchfor the suitable cell.

In the implementation of the present disclosure, when no suitable cellis searched out to reside in by a terminal device in the INACTIVE state,the terminal device may search for an acceptable cell and/or a suitablecell by entering an arbitrary cell search state, such that an existingprotocol framework can be applied as much as possible, and theapplicability is increased.

Furthermore, by specifying a state and context information of the UE, itcan be ensured that a UE's behavior is manageable and controllable.

A processing mode for a state and context information of the UE when theterminal device enters an arbitrary cell search state in theimplementation of the present disclosure is exemplarily explained below.

In one implementation, when entering the arbitrary cell search state,the terminal device starts a first timer; when the first timer expiresand no suitable cell is searched out, the terminal device enters an idlestate and deletes the context information; when the first timer does notexpire and the suitable cell is searched out, the terminal device stopsthe first timer and resides in the suitable cell.

Further, before the terminal device starts the first timer, the terminaldevice receives configuration information sent by the network device,wherein the configuration information is used for the terminal device toconfigure the first timer.

For example, the configuration information is information configured forthe terminal device when the network device instructs the terminaldevice to enter the inactive state.

In another implementation, when entering the arbitrary cell searchstate, the terminal device may directly enter the idle state and deletethe context information.

In another implementation, when entering the arbitrary cell searchstate, the terminal device continues to maintain the inactive state anda second timer, wherein the second timer includes a location updatetimer.

Further, when the second timer expires, the terminal device enters theidle state and deletes the context information.

It should be understood that in the implementation of the presentdisclosure, after the terminal device enters the idle state and deletesthe context information, the terminal device may further continue tomaintain the arbitrary cell search state.

It should further be understood that, when the terminal device entersthe arbitrary cell search state in the implementation of the presentdisclosure, the processing mode for the state and the contextinformation of the UE is only an exemplary description, andimplementations of the present disclosure are not limited to this.

For example, the terminal device may determine a specific processingmode according to a user requirement.

FIG. 3 is a schematic block diagram of a terminal device 300 accordingto an implementation of the present disclosure. It should be understoodthat the terminal device is in an inactive state, wherein the inactivestate refers to that the terminal device is disconnected from a networkdevice, both the network device and the terminal device retain contextinformation of the terminal device, and the context information is usedfor establishing a connection between the terminal device and thenetwork device.

As shown in FIG. 3, the terminal device 300 includes a processing unit310.

The processing unit 310 is configured to, when the terminal device doesnot search out any suitable cell to reside in, enter an arbitrary cellsearch state to search for an acceptable cell and/or a suitable cell,wherein the acceptable cell is a cell in which the terminal device iscapable of residing and only obtaining a restricted service, and thesuitable cell is a cell in which the terminal device is capable ofresiding and obtaining a normal service.

Optionally, the processing unit 310 is further configured to, when theterminal device searches out the acceptable cell, reside in theacceptable cell and continue to search for the suitable cell.

Optionally, the processing unit 310 is further configured to start afirst timer when the terminal device enters the arbitrary cell searchstate; when the first timer expires and no suitable cell is searchedout, enter an idle state and delete the context information; when thefirst timer does not expire and the suitable cell is searched out, stopthe first timer and reside in the suitable cell.

Optionally, the terminal device further includes a transceiving unit320.

The transceiving unit 320 is configured to receive configurationinformation sent by a network device before the processing unit 310starts the first timer, wherein the configuration information is usedfor the terminal device to configure the first timer.

Optionally, the configuration information is information configured forthe terminal device when the network device instructs the terminaldevice to enter the inactive state.

Optionally, the processing unit 310 is further configured to, when theterminal device enters the arbitrary cell search state, enter the idlestate and delete the context information.

Optionally, the processing unit 310 is further configured to, when theterminal device enters the arbitrary cell search state, continue tomaintain the inactive state and a second timer, wherein the second timerincludes a location update timer.

Optionally, the processing unit 310 is further configured to, when thesecond timer expires, enter the idle state and delete the contextinformation.

Optionally, the processing unit 310 is further configured to, after theterminal device enters the idle state and deletes the contextinformation, continue to maintain the arbitrary cell search state.

In the implementation of the present disclosure, the processing unit 310may be implemented by a processor, and the transceiving unit 320 may beimplemented by a transceiver. As shown in FIG. 4, a terminal device 400may include a processor 410, a transceiver 420, and a memory 430. Thememory 430 may be used for storing indication information, or may beused for storing codes, instructions, etc., executed by the processor410. The various components in the terminal device 400 are connected bya bus system. The bus system includes a power bus, a control bus and astatus signal bus in addition to a data bus.

The terminal device 400 shown in FIG. 4 can implement various processesimplemented by the terminal device in the method implementationsdescribed above. For avoiding duplication, the details will not berepeated herein. That is, the method implementations in implementationsof the present disclosure may be applied to a processor or implementedby the processor.

Specifically, in an implementation process, each act of the methodimplementations in the implementations of the present disclosure may beimplemented by an integrated logic circuit of hardware in the processoror an instruction in the form of software. More specifically, the actsof the method disclosed in connection with the implementations of thepresent disclosure may be directly embodied as completion through theexecution of a hardware decoding processor or completion through theexecution in the combination of hardware and software modules in thedecoding processor. Software modules may be located in a typical storagemedium in the art, such as, a random access memory (RAM), a flashmemory, a read-only memory, a programmable read-only memory, anelectrical erasable programmable memory, or a register. The storagemedium is located in the memory, and the processor reads the informationin the memory and completes the acts of the above method in combinationwith its hardware.

Herein, the processor may be an integrated circuit chip with acapability of processing signals, and may implement various methods,acts and logic block diagrams disclosed in the implementations of thepresent disclosure. For example, the above processor may be a generalpurpose processor, a digital signal processor (DSP), an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA) or other programmable logic devices, a transistor logic device,or a discrete hardware component, or the like. Furthermore, the generalpurpose processor may be a microprocessor or the processor may be anyconventional processor or the like.

In addition, the memory in implementations of the present disclosure maybe a transitory memory or non-transitory memory, or may include both thetransitory memory and the non-transitory memory. The non-transitorymemory may be a read-only memory (ROM), a programmable ROM (PROM), anerasable PROM (EPROM), an electrically erasable EPROM (EEPROM), or aflash memory. The transitory memory may be a Random Access Memory (RAM)which serves as an external cache. It should be understood that, theforegoing memory is an example for illustration and should not beconstrued as limiting. For example, optionally, the memory in theimplementations of the present disclosure may be a Static RAM (SRAM),Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM(DDR SDRAM), Enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), DirectRambus RAM (DR RAM), or the like. That is, memories in the systems andmethods described herein are intended to include, but are not limitedto, these and any other suitable types of memories.

Finally, it should be noted that the terms used in the implementationsof the present disclosure and the appended claims are for the purpose ofdescribing specific implementations only and are not intended to limitthe implementations of the present disclosure.

For example, the singular forms “a/an”, “said”, and “the” used inimplementations of the present disclosure and the appended claims areintended to include the plural forms unless the context clearlyrepresents other meanings.

For another example, depending on the context, word “when” as usedherein may be interpreted as “if” or “whether” or “while” or “inresponse to a determination of/that” or “in response to a detectionof/that”. Similarly, depending on the context, the phrase “ifdetermined” or “if detected (a stated condition or event)” may beinterpreted as “when . . . is determined” or “in response to adetermination” or “when (stated condition or event) is detected” or “inresponse to a detection of (stated condition or event)”.

Those of ordinary skill in the art will recognize that the exemplaryelements and algorithm acts described in combination with theimplementations disclosed herein can be implemented in electronichardware, or a combination of computer software and electronic hardware.Whether these functions are implemented in hardware or software dependson specific applications and design constraints of technical solutions.One skilled in the art may use different methods to implement thedescribed functions for each specific application, but suchimplementation should not be considered to be beyond the scope ofimplementations of the present disclosure.

Those skilled in the art may clearly understand that for convenience andconciseness of description, the specific working processes of thesystems, apparatuses and units described above may refer to thecorresponding processes in the method implementations and will not bedescribed here.

In several implementations provided by the present disclosure, it shouldbe understood that the disclosed systems, devices and methods may beimplemented in other ways. For example, the device implementationsdescribed above are only illustrative, for example, the division of theunits is only a logical function division, and there may be otherdivision modes in actual implementations, for example, multiple units orcomponents may be combined or integrated into another system, or somefeatures may be ignored or not executed. On the other hand, the mutualcoupling or direct coupling or communication connection shown ordiscussed may be indirect coupling or communication connection throughsome interfaces, apparatuses or units, and may be in electrical,mechanical or other forms.

The unit described as a separate component may or may not be physicallyseparated, and the component shown as a unit may or may not be aphysical unit, i.e., it may be located in one place or may bedistributed over multiple network units. Parts or all of the units canbe selected according to actual needs to achieve the purpose of theimplementations of the present disclosure.

In addition, various functional units in the implementations of thepresent disclosure may be integrated in one processing unit, or variousunits may be presented separately in a physical way, or two or moreunits may be integrated in one unit.

The function units may be stored in a computer readable storage mediumif realized in a form of software functional units and sold or used as aseparate product. Based on this understanding, the technical solutionsof the implementations of the present disclosure, in essence, or thepart contributing to the related art, or the part of the technicalsolutions, may be embodied in the form of a software product stored in astorage medium, including several instructions for causing a computerdevice (which may be a personal computer, a server, or a network device,etc.) to perform all or parts of the acts of the methods described invarious implementations of the present disclosure. The aforementionedstorage medium includes a medium capable of storing program codes, suchas, a U disk, a mobile hard disk, a read-only memory (ROM), a magneticdisk or an optical disk.

What are described above are merely the specific implementations of theimplementations of the present disclosure, but the protection scope ofthe implementations of the present disclosure is not limited thereto.Any change or substation that can be easily conceived by any one skilledin the art within the technical scope disclosed by the implementationsof the present disclosure shall be included within the protection scopeof the implementations of the present disclosure. Therefore, the scopeof protection of the implementations of the present disclosure should besubject to the scope of protection of the claims.

What is claimed is:
 1. A cell search method, comprising: searching, by aterminal device, a cell to camp on, wherein the terminal device is in aninactive state; searching, by the terminal device in the inactive state,for an acceptable cell and/or a suitable cell when the terminal devicedoes not find any suitable cell to camp on, wherein the acceptable cellis a cell on which the terminal device is capable of camping and onlyobtaining a limited service, and the suitable cell is a cell on whichthe terminal device is capable of camping and obtaining a normalservice; and when searching for an acceptable cell and/or a suitablecell, continuing to maintain, by the terminal device, the inactive stateand a timer, wherein the timer is a location update timer.
 2. The methodof claim 1, further comprising: when the acceptable cell is found,camping, by the terminal device, on the acceptable cell, and continuingto search for the suitable cell.
 3. The method of claim 1, furthercomprising: when searching for an acceptable cell and/or a suitablecell, starting, by the terminal device, a first timer; when no suitablecell is found before the first timer expires, entering, by the terminaldevice, an idle state and deleting the context information; or, when thesuitable cell is found before the first timer expires, stopping, by theterminal device, the first timer and camping on the suitable cell. 4.The method of claim 3, further comprising: before starting the firsttimer, receiving, by the terminal device, configuration information sentby the network device, wherein the configuration information is used forthe terminal device to configure the first timer.
 5. The method of claim3, further comprising: after entering the idle state and deleting thecontext information, continuing to maintain, by the terminal device,searching for an acceptable cell and/or a suitable cell.
 6. The methodof claim 4, wherein the configuration information is informationconfigured for the terminal device when the network device instructs theterminal device to enter the inactive state.
 7. The method of claim 4,further comprising: after entering the idle state and deleting thecontext information, continuing to maintain, by the terminal device,searching for an acceptable cell and/or a suitable cell.
 8. The methodof claim 1, further comprising: when the timer expires, entering, by theterminal device, an idle state and deleting the context information. 9.The method of claim 8, further comprising: after entering the idle stateand deleting the context information, continuing to maintain, by theterminal device, searching for an acceptable cell and/or a suitablecell.
 10. A terminal device, comprising a processor, wherein theprocessor is configured to search a cell to camp on, wherein theterminal device is in an inactive state; the processor is furtherconfigured to search for an acceptable cell and/or a suitable cell whenthe terminal device does not find any suitable cell to camp on, whereinthe acceptable cell is a cell on which the terminal device is capable ofcamping and only obtaining a limited service, and the suitable cell is acell on which the terminal device is capable of camping and obtaining anormal service; and the processor is further configured to, whensearching for an acceptable cell and/or a suitable cell, continue tomaintain the inactive state and a timer, wherein the timer is a locationupdate timer.
 11. The terminal device of claim 10, wherein the processoris further configured to, when the acceptable cell is found, camp on theacceptable cell and continue to search for the suitable cell.
 12. Theterminal device of claim 10, wherein the processor is further configuredto: start a first timer when the terminal device searches for anacceptable cell and/or a suitable cell; when no suitable cell is foundbefore the first timer expires, enter an idle state and delete thecontext information; or when the suitable cell is found before the firsttimer expires, stop the first timer and camp on the suitable cell. 13.The terminal device of claim 12, further comprising a transceiver,wherein the transceiver is configured to receive configurationinformation sent by the network device before the processor starts thefirst timer, wherein the configuration information is used for theterminal device to configure the first timer.
 14. The terminal device ofclaim 12, wherein the processor is further configured to: after theterminal device enters the idle state and deletes the contextinformation, continue to maintain searching for an acceptable celland/or a suitable cell.
 15. The terminal device of claim 13, wherein theconfiguration information is information configured for the terminaldevice when the network device instructs the terminal device to enterthe inactive state.
 16. The terminal device of claim 13, wherein theprocessor is further configured to: after the terminal device enters theidle state and deletes the context information, continue to maintainsearching for an acceptable cell and/or a suitable cell.
 17. Theterminal device of claim 10, wherein the processor is further configuredto: when the timer expires, enter an idle state and delete the contextinformation.
 18. The terminal device of claim 17, wherein the processoris further configured to: after the terminal device enters the idlestate and deletes the context information, continue to maintainsearching for an acceptable cell and/or a suitable cell.